Update spec/index.html

Co-authored-by: Ted Thibodeau Jr <[email protected]>

Author: pchampin

spec/index.html

@@ -304,7 +304,7 @@ <h3>RDF Vocabularies and Namespace IRIs</h3>
       the IRI <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral</code>
       would be abbreviated as <code>rdf:XMLLiteral</code>.
       Note however that such abbreviations are <em>not</em> meant to be processed directly as IRIs,
-      and must not be used in syntactic contexts where IRIs are expected.
+      and are not to be used in syntactic contexts where IRIs are expected.
       Note also that [=namespace IRIs=] and [=namespace prefixes=] are not a formal part of the RDF data model.
       They are merely a syntactic convenience for abbreviating IRIs;
       for processing, the actual IRIs are reconstructed by replacing each namespace prefix with the corresponding namespace IRI.